If I connect a LED :to LED+ it lights upto HSYNC it lights upto VSYNC it lights upto MPU it lights upto DISP it lights upto LED+ it lights upto CLK it lights a little bit upto R,G,B it lights up sometimes --> so I think I must see an output on the display

Is it now a software or a hardware Problem.It is possible that I have crushed the Display, but I don't think so.

When prototyping I highly recommend you focus on one section at a time, there's a lot to cover in your post.

First I would suggest trying to get your display operational in 16bit mode (default state when using the BB-BONE-LCD7-01-00A3.dts) and verify that your overlay has loaded / configured correctly.It would also be helpful to see your boot process if possible. To see the actual boot process a RS232 cable like the TTL-232R-3V3 from FTDI is needed. Just plug it into the J1 connector (located on the BBB) and open a serial terminal of your choice.

Second when posting a pinout table please be sure to include the pin numbers from the display to the BeagleBone Black.

e.g.Display : BBBPin 1 : LED- --> P8_3

Finally, it is extremely difficult to verify if your back-light circuit it correct without a schematic / wiring diagram.